Figure 73-2.

A hypothetical cellular differentiation pathway is used to illustrate the complexity of regulatory oversight of stem cell products. Mechanisms that control biologic processes such as self-renewal or lineage commitment include changes in gene and protein expression that lead to differentiation (steps in development, blue text) and interactions with the host through microenvironmental cell–cell interactions or growth factors (influences on development, green text). Regulatory concerns that are associated with these processes during in vitro stem cell manufacture are shown (black text). (Please see CD-ROM for color version of this figure.)